The purpose of the proposed research is to achieve a more complete understanding of vibratory analgesia, a sensory phenomenon--repeatedly documented in laboratory and clinic, but never subjected to comprehensive psychophysical study--in which pain reduction is achieved by vibrotactile cutaneous stimulation. In the proposed investigations it will be measured under a variety of experimental conditions, both in normally pain-free individuals, and in persons with temporomandibular disorders. Recently developed psychophysical scaling procedures will be employed to determine the dependence of vibratory analgesia on the frequency, amplitude, and location on the vibratory stimulus, and on the nature of the pain (whether clinical or experimental, and if the latter, whether tonic or phasic). Other experiments will answer questions about the characteristics of the pain-reduction process itself: whether it can block temporal summation of pain, whether it affects the discriminability and unpleasantness, as well as the perceived intensity of the pain, and whether it is enhanced when attention is focused on the vibratory stimulus. The results of the research will shed additional light on the fundamental nature of submodality interaction in somesthesis, and will also have implications regarding the optimization of vibratory analgesia as a clinical procedure.